Thanks Danny, that's a step in the direction I wanted to go.
But on further reflection, I think what I was looking for (i.e. have some class that stops it's own instantiation and defers to another class depending on some parameter value(s)) doesn't really make sense. Instead I need some sort of factory function that contains the conditionals and that returns an instance of the right class.
Cheers,
Kieron
On Jun 26, 2012, at 8:22, Danny Yoo <dyoo at hashcollision.org> wrote:
>> The solution that springs to mind is to choose which class to instantiate
>> with (if (list? param-a) ,,,) but then I'd have to state the parameter lists
>> twice.
>> Hi Kieron,
>>> Can you choose the class using an if or cond?
>> For example:
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> (define (try-it x)
>> (define the-class%
> (if (list? x) multi-item-representer% item-representer%))
>> (define r (new the-class% [param-a x] [param-b 50] [param-c "yellow"]))
>> (send r print))
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>> This bit of code binds the-class% at runtime to one of those classes,
> depending on x.